On a vehicle such as an automobile, various electronic control devices for engine control, for motor control, for automatic transmission control, and the like for example are mounted. As the electronic control device, there is one including a MOSFET for switching an inverter device, a DC-DC converter device, and the like, a capacitor module, and the like. Such electronic control device includes a circuit wiring board having plural solid wiring patterns and a chip component in which the electrodes formed in both ends are soldered to the wiring patterns.
Because an electronic control device for a vehicle is installed under an environment with sharp temperature change, solid wiring patterns and a chip component repeat expansion and shrinkage, and a crack is liable to occur in solder that connects the chip component and the wiring patterns to each other.
As a countermeasure for it, a surface mounting structure is known in which lands soldered to the electrodes of the chip component and wiring that connects the lands and the wiring patterns to each other are arranged in a circuit wiring board. With the surface mounting structure, it is assumed that the stress applied to the solder can be absorbed by making the width of the wiring narrower than the width of the chip component soldered to the land. The connection part of each land and the wiring is disposed within a region in which the region of the width of the chip component extends in the longitudinal direction or within a region in which the region of the length of the chip component extends in the transverse direction (refer to FIG. 1(a) of Patent Literature 1 for example).